1. Field of Invention
The present invention relates to a display apparatus, and, in particularly, relates to a transreflective display apparatus and driving method thereof.
2. Description of Related Art
There are more and more electronic devices have display devices, such as cell phones, personal digital assistants (PDAs), and laptop computers. The display devices are requested to be thin and/or light in order to save the volume and the cost of the electronic devices. To satisfy these requirements, various flat panel displays (FPDs) have been developed as alternatives to more conventional cathode ray tube displays.
The display panels of the FPDs are classified as transmissive display panels, reflective display panels, and transreflective display panels. The transmissive display panel uses a backlight module disposed at the back thereof to serve as a light source. The reflective display panel uses ambient light or a light source in the front of the panel. The transreflective display panel can use a backlight module and/or the ambient light as the light source.
FIG. 1 illustrates a diagram of a transreflective display panel. Each pixel of the transreflective display panel includes a reflective area, made of reflective material, and a transmissive area, made of transparent material. When the ambient light intensity around the display panel is strong enough, e.g. higher than a threshold value, the display panel is in a reflective mode that the ambient light is used as the light source and the display panel emanates lights from the reflective area. When the ambient light intensity is not strong, the display panel is in a transmissive mode that the backlight module is used as the light source and the display panel emanates lights from the transmissive area.
However, while the transreflective display panel is in the transmissive mode, the backlight module is started to provide a backlight, but the ambient light still exists to be reflected from the reflective area. Hence, some gray levels representing the darker pixels can not be displayed distinguishably. FIG. 2 shows a voltage-to-transparency (V-T) curve of the transreflective display panel. The dashed line L′ shows the distorted V-T curve, compared to the original solid line L without distortion. That is, while the voltage V0 is applied to the pixel, transparency T0′ of the distorted V-T curve L′ is actually displayed, instead of the expected transparency T0 in the original V-T curve L, due to the reflected ambient light. Therefore, the low gray levels corresponding below the transparency T0′ can not be distinguishably displayed as dark as desired. Therefore, it needs a good driving method for improving the above problems and further providing other advantages.